VSS and Dual-Active Detection over C3750 STACK using PAGP+

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Aug 10th, 2010
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Hi, I would like to use my core (C3750 stack) as the dual-active detection link for my VSS1400 cluster, the C3750 stack is MEC connected, Is that possible? and what releas should i use ?

Thank in advanced.....

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Jayakrishna Mada Wed, 08/11/2010 - 22:48
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Hi Magnus,

This is possible but it depends on how the MEC is connected on the 3750 stack. If you are having a cross stack etherchannel you cannot run pagp on the stack it has to be either mode on or mode LACP but if both the ports of MEC on the stack are on the same switch then you can use the PAGP+ or ePAGP.

Here is the link to the document that will help you configure it and also talks about other options (BFD and fast hello) along with the info that you are looking for:



MAGNUS SVENSSON Wed, 08/11/2010 - 23:35
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Thanks then I know.

One more question, Is there heavy load on the dual-active link in an dual-active state ?

I have experianced a crash of my dual-active switch (C4506) when my VSS1400 system lost al of its VSL links. The C4506 has client pc´s directly connected to it and has normal load.

Thanks in advance...

Magnus Svensson

Senior Security Consultant

Cygate AB

Röntgenvägen 2,Box 6084,SE-171 06 Solna, Sweden

+46 8 10 878 70 00

+46 8 10 8787 144

+46 76 7626 144

[email protected]


Jayakrishna Mada Thu, 08/12/2010 - 00:11
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No, there should not be any extra load on the MEC links of the down stream switches if dual-active recovery is configured if not the network instability could have caused the 4500 to crash. If there is a crash file on 4500 you can open a case with TAC team and have them analysize it.

But as I mentioned if you did not have dual-active recovery configured its possible that Active-Active situation caused that crash.



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